Solar modules, for example photovoltaic modules for generating electrical energy, or collector modules for heating thermal transfer media, are usually secured, when mounted on rooftops or on the ground, to profile rails arranged parallel to each other.
Mounting systems for solar modules must meet many different requirements. For example, they must be sufficiently strong to hold the modules, yet simultaneously have as little weight as possible so as not to exceed the load limits of roofs. It should also be possible to deploy the system as variably as possible on different substrates and it should also permit quick and easy mounting.
The object of the present invention is therefore to provide an improved mounting system which meets all these different kinds of requirements.
A first aspect of the present invention relates to a profile rail which comprises, in a cross-sectional view:                a support surface forming a flat bottom side of the profile rail,        a first and a second receiving space, each having a lateral opening, said openings facing in opposite directions,        a third receiving space in the form of a T-slot having an opening facing away from the bottom side of the profile rail, said opening being defined by two webs which are mirror-symmetrical relative to a mentally conceived center plane and which are each cranked inwards at their respective free end,        a first rectangular, central hollow space, enclosed on all sides, which is defined by the support surface and by the first, second and third receiving space, and        a first and a second hollow lateral space, enclosed on all sides, arranged on opposite sites of the third receiving space and each adjoining one of the first and second receiving spaces.        
The profile rail according to the present invention is particularly light, yet is also very stable. Profile rails generally account for up to 98% of the weight of attachment systems for solar modules, a reduction in the weight of the profile rails has a strong effect on the total load exerted by an attachment system. Due to the third receiving space being designed in the form of a T-slot with webs having cranks, the profile rail according to the invention is suitable not only for receiving special components with hooks, but also for receiving standard connectors, such as T-head bolts and trapezoidal nuts, and thus for quick and easy mounting.
A particularly advantageous embodiment of the profile rail is one in which the height of the first central rectangular hollow space above the support surface is greater than the height of the first and the second receiving space above the support surface, such that the first central hollow space overlaps the first and the second lateral hollow space on either side. This gives the profile rail additional stability.
It is also advantageous when the first and second receiving spaces are likewise designed in the form of a T-slot, as this allows not only special components but also standard connectors such as T-slot bolts and trapezoidal nuts to be used for mounting.
It is also advantageous when the profile rail has lateral external walls which have a toothed profile in whole or in part. By using toothed profiles, it is possible to prevent abutting components from slipping, especially during the mounting process.
A second aspect of the invention relates to a clip holder, comprising:                a head plate having a threaded hole and        two legs laterally disposed on the head plate, wherein the ends of said legs, facing away from said head plate, have hooks which are designed to engage cranks in the profile rail.        
Such a clip holder can be inserted into the third receiving space in the inventive profile by exerting slight pressure and can still be moved within the rail until final mounting. This can be carried out in a particularly advantageous manner using a clip holder in which the hooks slope inwards to an inner side of the respective leg by an angle of 15° to the horizontal. If a module is seared with the aid of such a clip holder and a screw, the screw fastens itself into the clip holder inserted into the profile rail, and said clip holder secures itself as a result of the hooks sloping at an angle of 15°.
In one advantageous variant of the invention, the head plate of the clip holder is square in the plan view. With the aid of such clip holders, the profile rails can be arranged in a particularly advantageous manner at an angle of 90° to the solar modules, and also in the joint between two modules.
A third aspect of the invention relates to a cross-connector which comprises, in a cross-sectional view:                a middle web having a right-angled end and a beveled end,        a first L-shaped extension attached to the middle web closer to the right-angled end than to the beveled end, and        a second L-shaped extension attached to the middle web closer to the beveled than to the right-angled end and attached to the side of the middle web opposite the first L-shaped extension.        
The cross-connector allows profile rails arranged perpendicular to each other to be joined together easily and securely.
A fourth aspect of the invention relates to an attachment system for solar modules, comprising:                a number of profile rails according to the invention and        a plurality of clip holders according to the invention, in which the hooks have shapes complementary to the cranks in the profile rails,wherein the plurality of clip holders are inserted in the third receiving spaces of the profile rails and the hooks of the clip holders engage the cranks in the profile rails and wherein retention members are secured to the clip holders by means of screws inserted into the threaded holes.        
Such an attachment system has a lower weight than solutions known hitherto, and it is possible with such an attachment system for solar modules to be mounted quickly and straightforwardly. The profile rails are mounted on a roof or a stand structure, after which the first solar modules can be put in place. The clip holders are then inserted with slight pressure into the third receiving space of the profile rails and can then be brought to their final position by sliding them accordingly. Other adjacent solar modules can then be mounted and, by tightening the screws, the solar modules can be collectively fixed in place using the retention members. However, the attachment system according to the invention also allows all the solar modules to be put in place to begin with, after which the clip holders with retention members attached thereto are inserted between the adjacent solar modules.
In one advantageous development of the invention, the attachment system includes at least two profile rails arranged perpendicular to each other in such a way that a cross-connector having the first L-shaped extension according to the invention is received in the first or in the second receiving space of the one profile rail and is secured by use of the second L-shaped extension by means of a screw to a clip holder which for its part is inserted in the third receiving space of the second profile rail. A secure connection between profile rails arranged perpendicular to each other can thus be achieved in an easy manner.
To install larger areas of solar modules, the profile rails can be joined together, in another advantageous development of the attachment system according to the invention, via a telescopic connector which is received in the first central hollow space in each of the two profile rails. In its simplest form, said telescopic connector is manufactured in the form of a square tube, the outside dimensions of which correspond to the inside dimensions of the first central hollow space of the profile rails being connected.
The advantages specified above in respect of the profile rails, the clip holder or the cross-connector also apply for an attachment system according to the fourth aspect of the invention.